1. Field of the Invention
The present invention relates to a planetary bearing structure applied to, for example, the gearbox of a wind power generator. 2. Description of Related Art
A wind power generator is an apparatus that generates electricity with a generator that is driven in such a manner that a rotor head equipped with wind turbine blades rotates when receiving wind power and increases the rotational speed using a gearbox.
An example of the gearbox that increases the rotational speed of the rotor head is a planetary gear speed increasing mechanism. This planetary gear speed increasing mechanism is equipped with a plurality of planetary gears mounted to a carrier that rotates together with an input shaft and is configured such that these planetary gears engage with a sun gear that rotates together with an output shaft and internal gears fixed to the housing of the gearbox to revolve. In other words, the planetary gear speed increasing mechanism is an apparatus that increases the rotational speed of the carrier joined to the input shaft in accordance with the gear ratio set for the planetary gears, the sun gear, and the internal gears (the revolving speed of the planetary gears) and outputs the rotation from the output shaft joined to the sun gear.
The planetary gears of the planetary gear mechanism described above are each rotatably supported by the carrier via a planetary bearing. A rolling bearing or a slide bearing is generally used as the planetary bearing.
Between them, in a planetary bearing structure that employs the slide bearing, a slide bearing 50 is mounted to the inner peripheral surface of a planetary gear 40, for example, as shown in FIG. 11, and rotates about the outer periphery of a planetary pin 30 fixed to a carrier 21 side. At that time, the sliding surface between the slide bearing 50 and the planetary pin 30 generates pressure of lubricant oil in the bearing due to the rotation of the slide bearing 50 together with the planetary gear 40. This can therefore prevent the sliding surface of the slide bearing 50 from coming into contact with the planetary pin 30 owing to the pressure of the lubricant oil.
In the case where the slide bearing 50 is employed as the planetary bearing, a lubricating structure that reliably supplies lubricant oil to the sliding surface with a lubricant oil pump (not shown) or the like is employed because it is generally necessary to forcedly supply oil to the bearing portion.
With a planetary bearing structure shown in FIG. 11, a lubricant oil channel 60 extending from the carrier 21 and passing through the axial center of the planetary pin 30 is formed, as indicated by the broken line in the drawing, to supply lubricant oil to the sliding surface of the slide bearing 50 from an oil supply unit (not shown). This lubricant oil channel 60 has an oil supply port 61 in the radial direction formed in the planetary pin 30 to supply the lubricant oil to an oil supply groove 31 provided in the outer peripheral surface of the planetary pin 30. Reference sign 31a in the drawing denotes a chamfer formed at both axial ends of the oil supply groove 31.
A known slide bearing lubricating structure for forced lubrication is a technology for preventing wear and seizure of the bearing surface by checking the circulation of lubricant oil that has increased in temperature through the bearing to thereby prevent an increase in the temperature of the lubricant oil. In this technology, an oil supply groove that is axially elongated is formed in the arc-shaped surface of the bearing, and a brush seal that is axially elongated is fitted in the downstream edge of each bearing. (For example, refer to FIG. 1 of Japanese Unexamined Patent Application, Publication No. Hei 10-103344)
Furthermore, for a journal bearing, discharging solid foreign matter in a bearing main body to the outside of the bearing main body by positively using the flow of lubricant oil due to the rotation of a rotation shaft has been proposed (for example, refer to Japanese Unexamined Patent Application, Publication No. 2000-337360).
Meanwhile, in the case where the slide bearing 50 is used as the planetary bearing, when the rotational speed of the slide bearing 50 that rotates together with the planetary gear 40 becomes low, the planetary pin 30 inevitably comes into contact with the sliding surface of the slide bearing 50. Therefore, a soft alloy or plastic-based material is employed as a material for use in the sliding surface of the slide bearing 50.
However, since the sliding surface (bearing surface) and the planetary pin 30 inevitably come into contact with each other, friction occurs on the sliding surface of the slide bearing 50. As a result, wear debris of the sliding surface material is generated on the sliding surface of the slide bearing 50, which further accelerates wear by catching the wear debris unless the wear debris is smoothly discharged from the sliding surface of the slide bearing 50.
Since such accelerated wear finally causes damage to the slide bearing 50, it is desired to take measures to improve the durability and reliability of the planetary bearing.
The present invention is made in consideration of the above-described circumstances, and it is an object thereof to provide a planetary bearing in which a slide bearing is used as the bearing portion having a planetary bearing structure capable of smoothly discharging wear debris that is generated due to the contact between the bearing surface and the planetary gear together with lubricant oil from the sliding surface (bearing surface).